The invention relates generally to dual cure compositions, methods of curing, and resulting articles.
Formation of thick sections by curing of thermoset resins (sometimes referred to hereinafter as curable monomers) has been generally problematic. Most traditional thermally cured reactive formulations have short work-life and long cure time. On the other hand, photocured formulations have long work-life and are capable of rapid cure, but curing is limited by the penetration depth of UV light, especially in materials with high levels of fillers which absorb or block UV light, such as in thick section composites, composite sandwich structures, and carbon fiber composites, thus resulting in uncured or incompletely cured portions. Curing thick carbon fiber composites has been demonstrated with e-beam technology. However, e-beam uses a high energy source which requires high cost capital investment.
The problems described have been addressed by the use of compositions comprising monomers that are cured by one or more energy sources. The cured compositions are typically derived from monomers having ethylenic units, isocyanate units, ester units, or the like, or combinations thereof. Curing of some of the compositions results in evolution of gases, which may become entrapped in the composition thus compromising some of the properties of the product. Also, the curing methods result in inefficient energy usage. Alternatively, thick sections have been formed by joining multiple precured panels or plies. But this results in bond lines. Thus, there is a need in the art to develop novel curable compositions and more efficient and cost-effective methods to fabricate thick sections, structures and articles.